Why don't notifications clear automatically?

[mcdj]

i'm sure this has been asked. I can't find the answer. Why doesn't the Apple Watch clear notifications automatically when I read a message on another device? Isn't the red dot essentially the same as a notification badge? Notification badges disappear automatically on all my devices when a message has been read on any other device. Why not the Apple Watch?

 

[AS90]

I hate the way I raise to read a message but the red dot stays after I have read it.